In producing press plates for printing books or the like, it has so far been carried out to print together a plurality of originals corresponding to, in general, from 8 to 32 pages on one sheet of press plate from the standpoints of printing efficiency and printing cost (See FIG. 1, wherein numeral numbers stand for the page numbers to be printed respectively).
In such a case, press plates of A-size (625 mm.times.880 mm) or B-size (766 mm.times.1085 mm) are produced corresponding respectively to whether the size of an intended print is included in the A-series or B-series sizes.
If the photographing of such a great-size picture is intended with an apparatus miniaturized to the greatest possible extent, it is required to use a lens having a wide angle of view and ensuring the highest possible extent of-image reproduction in not only the center part of the picture to be photographed but also the peripheral area thereof. As well known, however, it causes various types of aberration problems to leave a lens as it is small in diameter, notwithstanding the increase in picture area to be photographed with said lens. Therefore, it is requested to use a lens having a great diameter. In case the diameter of a lens is increased, on the other hand, the production cost of the lens rises steeply. Accordingly, it is quite natural from the economical point of view that there is a limit in the diameter of a lens applicable to the photographing apparatus. Under these circumstances, sacrifices of resolution and reproducibility of images have so far been made.
In the meantime, it has hitherto been considered that the greatest possible reduction in size of a picture to be photographed and the use of a lens having a focal length long enough to cover the whole area of the picture was desirable for the purpose of heightening image resolving power and image reproducibility, as described in Japanese Jikko Hei 6-22836 (the term "Jikko" as used herein means an "examined utility model publication"). This measure however has disadvantages in that it is difficult to miniaturize the photographing apparatus and the apparatus cannot help rising in price.
As a result of our intensive studies of the above-described problems, it has been found out that when there is adopted a method which comprises arranging two separate mirrors so that they may reflect respectively thereon the reflected rays coming separately from the left half and the right half of an original and making the rays reflected by the separate mirrors irradiate the front and the back sides of one convex lens respectively, a lens having a focal length reduced to one-half that of the lens required conventionally for the photographing of a picture with a given size can cover a picture increased in size by a factor of two to result in realization of a miniaturized photographing apparatus of high resolving power, thereby achieving the present invention.